Apple Inc.
SURFACE NANOGRAIN FOR IMPROVED DURABILITY OF METAL BANDS

Abstract:

A housing for an electronic device can include a metallic component at least partially defining an external surface of the device. The metallic component can have an average grain size less than 45 nanometers in a first region that extends from the external surface to a depth of at least 100 microns below the external surface, and an average grain size greater than 45 nanometers in a second region adjacent to the first surface.